1. Field of the invention
The present invention relates to an induction charging apparatus for charging battery means in an electronic device when inductively coupled to the charging apparatus, the charging apparatus comprising a first casing having a charging receptacle for receiving the electronic device and an alternating current power source coupled to a primary coil provided in the first casing, and the electronic device comprising a second casing provided with a secondary coil electronically coupled to the battery means, whereby the primary and the secondary coil are magnetically coupled for inductively conveying energy from the primary coil to the secondary coil when the electronic device is put in the receptacle
The present invention further relates to an electronic device having battery means to be charged by means of the induction charging apparatus. Such an electronic device can be a cordless or a cellular telephone, or any other electronic device powered by means of batteries.
2. Description of the related art
An induction charging apparatus and an electronic device of this kind are known from the European patent application EP 0 642 203 A1. In this European patent application an induction charging apparatus is described having a depressible member movably provided and closing an open end of a casing of the charging apparatus forming a charging receptacle for an electronic device when batteries in the electronic device are to be charged by means of the charging device. Charging is done by inductively conveying energy from a primary coil comprised in the charging apparatus to a secondary coil comprised in the electronic device and rectifying an alternating current so generated in the secondary coil. When the electronic device is absent from the charging receptacle, the depressible member is in a raised position in which magnetic fluxes generated in the primary coil are substantially located under the depressible member. When the electronic device is present in the charging receptacle, the depressible member is in a depressed position, the generated magnetic fluxes are substantially located over the depressible member so that substantial energy can be conveyed from the primary to the secondary coil. Herewith, the problem of a metallic object, such as a paper clip, being heated by eddy currents generated by the flux of the primary coil when such a metallic object is in the vicinity of the primary coil when the electronic device is absent is said to be solved. Now that cordless and cellular phones are becoming lighter and lighter, such phones would get weights comparable to metallic objects a person is carrying with him, such as a bunch of keys, or the like. Then, a spring constant of a spring counteracting the force exerted by the phone on the depressible member when the phone is put in the charging receptacle would have a value such that also relatively light metallic objects would depress the depressible member to such an extent that the flux would no longer be substantially located under the depressible member. Herewith, the danger of undesired heating of metallic objects is still present. Besides, the solution proposed in said European patent application is a complicated and vulnerable mechanical solution making the induction charging apparatus relatively expensive and difficult to manufacture.